Materials of high dielectric constants, such as SrTiO3, Pb(Zr,Ti)O3, etc. are expected to be used in the electronic field of semiconductor memories, etc.
For example, a usual DRAM comprises cells each including one transistor and one capacitor. For high integration, it is effective to reduce an area of the capacitors. To reduce the area of the capacitors, it is effective to use a film having a dielectric constant higher than the dielectric constants of silicon oxide film, ONO film (of the three-layer structure of silicon oxide film/silicon nitride film/silicon oxide film), or etc. This enables the device to be further micronized and more integrated
The deposition of SrTiO3 film, (Ba,Sr)TiO3, and Pb(Zr,Ti)O3 films is usually conducted in an oxidizing atmosphere. Accordingly, the base electrode must be formed of a material which is hard to be oxidized or a material which can maintain conductivity even when oxidized. The conventional electrode is made of platinum (Pt), which is hard to be oxidized.
An upper electrode to be formed on the SrTiO3 film or Pb(Zr,Ti)O3 film must be formed also of an oxidation resistant material. Unless an oxidation resistant material is used, oxygen atoms contained in the SrTiO3 film or Pb(Zr,Ti)O3 film are absorbed by the upper electrode to adversely increase leak current flowing in the dielectric film.
In forming such capacitors on a silicon substrate, a diffusion preventive film of Ti film, TiN film or others is provided between the silicon substrate and the Pt film as the lower electrode.
This is because in depositing the Pt film directly on the silicon substrate, silicon atoms in the silicon substrate are diffused in the Pt film and arrive at the surface of the Pt film in depositing the dielectric film, and a silicon oxide film is adversely formed on the interface between the dielectric film and the Pt film, and the formed capacitors have a decreased capacitance.
Thus, the capacitor devices formed of a high dielectric thin film are formed, reducing diffusion of silicon atoms from the silicon substrate.
Platinum film used as an electrode of a high dielectric constant material, such as SrTiO3, (Ba,Sr)TiO3, or others, is deposited mainly by sputtering.
FIG. 45 shows one example of sputtering apparatuses. In a deposition chamber 384 a target 386 of platinum and a substrate 388 for a platinum film to be deposited on are opposed to each other. A direct current source 390 is connected to the target 386 and the substrate 388, and a high negative voltage can be applied to the target 386 as the cathode. An Ar (argon) gas feed pipe 392 is connected to the deposition chamber 384, and Ar gas as a sputtering gas can be fed into the deposition chamber 384. A substrate holder 394 includes a heater 396 which heats the substrate 388 as required for the deposition.
Next, the method for depositing a platinum film by sputtering will be explained.
First, the pressure of the interior of the deposition chamber 384 is decreased by evacuation by a vacuum pump (not shown) through an exhaust port 398, and then Ar gas is fed into the deposition chamber 384 through the Ar gas feed pipe 392 to establish a pressure in the deposition chamber 384. For example, an Ar gas flow rate is set at 100 sccm to establish a pressure of 1-5xc3x9710xe2x88x923 Torr.
Then a direct voltage is applied between the substrate 388 and the target 386 to generate Ar plasma. Dissociated Ar ions collide on the target 386 as the cathode and sputter platinum atoms. The sputtered platinum atoms arrive at the substrate 388 and deposit a platinum film on the substrate 388.
Thus a platinum film is deposited by sputtering.
As an electrode for high dielectric constant materials, such as SrTiO3, (Ba,Sr)TiO3, etc., iridium film or iridium oxide film other than platinum film are used.
Also in the conventional fabrication process for semiconductor devices, in which iridium film is deposited, sputtering is mainly used for the deposition of platinum film.
Recently Japanese Patent Laid-Open Publication No. 290789/1994 proposes a method for depositing iridium film by CVD using an organic compound of iridium.
Iridium film or iridium oxide film deposited by sputtering or CVD must be patterned in accordance with their applications, but because iridium film or iridium oxide film do not generate reactive products of high vapor pressures, it is difficult to use iridium film or iridium oxide film in a patterning method, such as RIE (Reactive Ion Etching), which uses reactions.
To pattern iridium film or iridium oxide film, the so-called ion milling, by which a target is processed physically by collision of ions, is used.
Furthermore, as an electrode of high dielectric constant material, such as SrTiO3, (Ba,Sr)TiO3, etc., ruthenium film or ruthenium oxide film are used in some cases.
In the conventional fabrication processes for semiconductor devices, sputtering or CVD is mainly used in depositing ruthenium film or ruthenium oxide film, Especially CVD is recently noted because ruthenium film or ruthenium oxide film can be deposited in a uniform thickness on the tops and sides of the steps of stepped patterns.
For the deposition of ruthenium film or ruthenium oxide film by CVD, 2,3,6,6-Tetramethyl 3,5-heptanediene Ruthenium, hereinafter abbreviated as Ru(DPM)3, is used as a ruthenium source material.
Ru(DPM)3 is a pulverized solid at room temperature, and to be used for CVD, it must be vaporized. Ru(DPM)3 is vaporized in the following procedure.
First, powder Ru(DFM)3 is loaded in a vessel for low vapor pressure and is place in a thermostatic oven. Then, the interior of the thermostatic oven is heated up to the sublimation temperature of Ru(DPM)3 to sublimate the Ru(DPM)3. Subsequently the sublimated Ru(DPM)3 is bubbled by an inactive gas to be fed into the deposition chamber together with the inactive gas.
The gas thus fed into the deposition chamber is decomposed and reacted on a substrate which has been heated to about 300xc2x0 C. and retained at 300xc2x0 C., and ruthenium film is deposited on the substrate.
Ruthenium oxide film is deposited on the substrate to feed the sublimated Ru(DPM)3 together with oxygen gas.
However, in the above-described conventional fabrication methods for capacitor devices, diffusion of silicon atoms can be prevented by a diffusion preventive film, but in depositing the dielectric film, oxygen atoms are diffused in the Pt film to arrive at the diffusion preventive film, oxidizing the diffusion preventive film.
Such oxidation of the diffusion preventive film disenables contact between the Pt film and the silicon substrate, and devices directly below the capacitors cannot contact with them each other, with a result that high integration is impossible,
In a case that Pt film is used as the electrode, the Pt film cannot be patterned by RIE, and must be patterned by ion milling. Ion milling, however, is inferior to RIE in processing precision and throughput.
The thin film depositing method for depositing platinum film, iridium film or iridium oxide film or others by the above-described conventional sputtering has the problem of being unable to deposit platinum film on the tops and sides of the steps of a stepped pattern drawn on the substrate in a uniform thickness.
Accordingly, it is difficult to deposit a platinum film, iridium film or iridium oxide film on complicated patterns, which makes it impossible to use platinum film, iridium film or iridium oxide film as electrodes of high dielectric constant materials of thin capacitor cells, or stacked capacitor cells of DRAMs (Dynamic Random Access Memory).
The iridium film deposited by the thin film depositing method described in Japanese Patent Laid-Open Publication No. 290789/1994 has much better covering on step-patterned substrates than that deposited by sputtering. In a case that iridium acetylacetate, for example, is used as a iridium source material, it is difficult to stably supply the gas, which causes a large disuniformity of thickness of the deposited iridium film, In addition to this, no iridium source material which can reduce the thickness disuniformity of the iridium film in its deposition by CVD has been found.
Furthermore, it is difficult to make micronized patterns in iridium film or iridium oxide film by the above-described conventional ion milling, and iridium film or iridium oxide film is difficult to be applied to device processes, as of DRAMs, which require micronized processing.
From this viewpoint, the selective growth of iridium film and iridium oxide film is preferable, but the possibility of their selective growth under the conventional film forming conditions has not been found.
In the above-described conventional film depositing method for ruthenium or ruthenium oxide film, because Ru(DPM)3 is sublimated at a temperature (about 135xc2x0 C.) below its melting point (160-170xc2x0 C.), it is difficult to feed Ru(DPM)3 into the deposition chamber in a constant feed amount.
That is, a feed amount of Ru(DPM)3 depends on an area of contact between the Ru(DPM)3 and its carrier gas. Ru(DPM)3 powder decreases as a deposition time lapses, and the area of the contact therebetween decreases. A feed amount of Ru(DPM)3 often decreases as a deposition time lapses.
In addition, due to non-constant feed amounts of the raw material, the deposited ruthenium films or ruthenium oxide films vary in film thickness and sheet resistance among batches.
A first object of the present invention is to provide a capacitor device, a dielectric film of which can be deposited in an oxidizing atmosphere without deteriorating characteristics thereof and a fabrication method for fabricating the same, and a semiconductor device.
A second object of the present invention is to provide a capacitor device structure which allows processing precision of the electrode to be improved and throughput to be improved, and a semiconductor device.
A third object of the present invention is to provide a thin film deposition method which can deposit by CVD platinum film having a good covering on the surfaces of steps, and a semiconductor device using platinum film and a fabrication method for fabricating the same.
A fourth object of the present invention is to provide a thin film depositing method Which can deposit stable ruthenium film or ruthenium oxide film by stably feeding ruthenium source material.
A fifth object of the present invention is to provide a highly reliable semiconductor device using ruthenium film or ruthenium oxide film deposited by the thin film depositing method, and a fabrication method for fabricating the same.
A sixth object of the present invention is to provide a thin film depositing method which can deposit iridium film and iridium oxide film having little film thickness disuniformity by CVD which is superior in covering on the surfaces of steps, a semiconductor device using the iridium film or iridium oxide film and a fabrication method for fabricating the same.
A seventh object of the present invention is to provide a thin film depositing method which can selectively grow iridium film and iridium oxide film.
An eighth object of the present invention is to provide a semiconductor device having iridium film or iridium oxide film with a micronized pattern formed by selectively growing the iridium film or iridium oxide film and a fabrication method for fabricating the same.
The above-described objects are achieved by a capacitor device comprising a pair of electrodes, and a dielectric film formed between the pair of electrodes, at least one of the pair of electrodes being formed of a material containing titanium nitride of (200) orientation, whereby even in a case that a high dielectric film formed in an oxidizing atmosphere is used as the capacitor dielectric film, the capacitor device can have good quality. By forming the electrodes of the capacitor device of titanium nitride, the electrodes can be patterned by RIE. Processing precision of the electrodes and throughputs can be much improved.
The above-described objects are achieved by a capacitor device comprising: an insulating film formed on a substrate, and having a contact hole reaching the substrate; a first electrode formed on the insulating film, and electrically connected to the substrate through the contact hole formed in the insulating film; a dielectric film formed on the first electrode; a second electrode formed on the dielectric film; a first diffusion preventive film formed between the substrate and the first electrode for preventing a material forming the substrate from diffusing toward the first electrode; and a second diffusion preventive film formed between part of the first electrode in a region having the contact hole formed therein and the dielectric film for preventing oxygen in an oxidizing atmosphere from diffusing toward the first electrode, whereby even in forming the dielectric film in an oxidizing atmosphere, the first diffusion preventive film is not oxidized, and accordingly a contact resistance between the first electrode and the substrate can be kept low.
It is preferred that the above-described capacitor device further comprises an oxidation-resistant conducting film provided between the second diffusion preventive film and the dielectric film, whereby oxidation of the first diffusion preventive film can be prevented without decrease in capacitance caused by the second diffusion preventive film.
The above-described objects can be achieved by a semiconductor device comprising a memory cell including the above-described capacitor device; and a transistor electrically connected to one of the electrodes of the capacitor device, whereby the semiconductor device can be formed in a small region with a large capacitance, and accordingly its storage capacitance and integration can be improved.
The above-described objects are achieved by a method for fabricating a capacitor device comprising a first diffusion preventive film forming step of forming a first diffusion preventive film on an insulation film formed on a substrate and having a contact hole reaching the substrate formed therein for preventing a material forming the substrate from diffusing toward a device to be formed on the insulation film; a first electrode forming step of forming a first electrode on the first diffusion preventive film, a second diffusion preventive film forming step of forming a second diffusion preventive film on part of the first electrode in a region having the contact hole formed therein for preventing oxygen from diffusing in the second diffusion preventive film; a dielectric film forming step of forming in an oxidizing atmosphere a dielectric film on the first electrode having the second diffusion film formed thereon; and a second electrode forming step of forming a second electrode on the dielectric film, whereby in forming the dielectric film in an oxidizing atmosphere, the oxidation of the first diffusion preventive film is prevented, and a contact resistance between the first electrode and the substrate can be maintained low.
It is preferred that the above-described method for fabricating a capacitor device further comprises a conducting film forming step of forming an oxidation resistant conducting film on the first electrode having the second diffusion preventive film formed thereon, which step follows the second diffusion preventive film forming step, whereby the oxidation of the first diffusion preventive film can be prevented without decreasing the capacitance of the second diffusion preventive film.
The above-described objects are achieved by the thin film forming method in which a platinum film is formed by chemical vapor deposition using Pt(HFA)2 as a source material, whereby platinum film can be formed with good covering even on rough surfaces of substrates.
It is preferred that in the above-described thin film forming method, a substrate for the platinum film to be formed on is heated to 300-600xc2x0 C.; and a reaction pressure in a film forming chamber in which the platinum film is formed is set to 1-20 Torr, whereby the platinum film can have good quality.
It is preferred that in the above-described thin film forming method hydrogen gas is fed into the film forming chamber in which the platinum film is formed when the platinum film is formed, whereby less carbon is mixed into the platinum film, and high quality platinum film having good orientation can be formed.
The above-described objects are achieved by the method for fabricating a semiconductor device comprising the step of forming a platinum film by the above-described thin film forming method, whereby high quality platinum film can be formed, and the semiconductor device can have improved reliability.
The above-described objects are achieved by the thin film forming method in which ruthenium film or ruthenium oxide film is formed by chemical vapor deposition using Ru(DMHPD)3 as a source material. Ruthenium or ruthenium oxide film is thus formed, whereby the ruthenium source material can be stably supplied. Accordingly, good control is possible, and the ruthenium film or the ruthenium oxide film can be deposited without deviations among batches.
It is preferred that in the above-described thin film forming method, the Ru(DMHPD)3 is liquidized and vaporized for use, whereby by vaporizing Ru(DMHPD)3, the inert gas and the Ru(DMHPD)3 contact each other with a substantially constant area, and the Ru(DMHPD)3 can be stably supplied.
It is preferred that in the above-described thin film forming method, a substrate for the ruthenium film or the ruthenium oxide film to be formed on is heated to 300-500xc2x0 C.; and a reaction pressure in a film forming chamber in which the ruthenium film or the ruthenium oxide film is to be formed in is set to 1-10 Torr. The thus-formed ruthenium film or ruthenium oxide film can have good quality.
It is preferred that in the above-described thin film forming method, hydrogen gas is fed into a film forming chamber in which the ruthenium film is formed when the ruthenium film is formed. By feeding hydrogen gas into the film forming chamber in forming ruthenium film, less carbon is mixed into the ruthenium film, and accordingly the ruthenium film can have good quality.
It is preferred that in the above-described method, oxygen gas is fed into a film forming chamber in which the ruthenium oxide film is formed when the ruthenium oxide film is formed.
The above-described objects are achieved by the semiconductor device comprising the ruthenium film or the ruthenium oxide film formed by the above-described thin film forming method.
The above-described objects are achieved by the method for fabricating a semiconductor device comprising the step of forming the ruthenium film or ruthenium oxide film by the above-described thin film forming method, whereby in the step of forming the ruthenium film or the ruthenium oxide film, deviations between batches can be reduced.
The above-described objects are achieved by the thin film forming method in which iridium film or iridium oxide film is formed by chemical vapor deposition using Ir(DPM)3 as a source material. By thus depositing iridium film or iridium oxide film, the iridium film or the iridium oxide film can be deposited with good covering even on rough surfaces of substrates; In comparison with the deposition of iridium film or iridium oxide film by the conventional use of Ir(acac)3 as a source material, thickness deviations of the film can be kept small.
It is preferred that in the above-described thin film forming method, a substrate for the iridium film or the iridium oxide film to be formed on is heated to 500-600xc2x0 C.; and a reaction pressure in a film forming chamber in which the iridium film or the iridium oxide film to be formed in is set to 1-20 Torr. By thus forming the iridium film or the iridium oxide film, the iridium film or the iridium oxide film can have good quality.
It is preferred that in the above-described thin film forming method, hydrogen gas is fed into the film forming chamber in which the iridium film is formed when the iridium film is formed, whereby the iridium film can have little carbon mixed in, and a resistivity of the iridium film can be much decreased, The iridium film can have improved flatness.
It is preferred that in the above-described thin film forming method, oxygen gas is fed at a 0.5-16 Torr partial pressure into the film forming chamber in which the iridium oxide film is formed when the iridium oxide film is formed. By thus depositing the iridium oxide film, the iridium oxide film can have good quality.
The above-described objects are achieved by the above-described thin film forming method, in which the iridium film or the iridium oxide film is selectively deposited in a first region of substrate for the iridium film or the iridium oxide film to be deposited on said first region, a first material being exposed, the substrate having the first region and a second region with a second material exposed. The thus selectively formed iridium film or the iridium oxide film does not need patterning by ion milling. Iridium film or iridium oxide film having micronized patterns can be easily formed.
It is preferred that in the above-described thin film forming method, in depositing the iridium film, the substrate for the iridium film to be deposited on is heated to a temperature above 400xc2x0 C. and below 550xc2x0 C., and the interior of the film forming chamber is set at a pressure above 0.1 Torr and below 20 Torr. Iridium film can be selectively grown by thus setting thin film forming conditions.
It is preferred that in the above-described thin film forming method, in depositing the iridium oxide film, the substrate for the iridium oxide film to be formed on is heated to a temperature above 400xc2x0 C. and below 600xc2x0 C., and the interior of the film forming chamber is set at a pressure above 0.1 Torr and below 30 Torr. Iridium oxide film can be selectively grown by thus setting the thin film forming conditions.
The above-described objects are achieved by a method for fabricating a semiconductor device comprising: a barrier layer forming step of forming a barrier layer of Ti film or TiN film in a first region of a substrate; a lower electrode forming step of selectively depositing iridium film or iridium oxide film on the barrier layer by the above-described thin film forming method to form a lower electrode; a dielectric film forming step of forming a dielectric film on the lower electrode; and an upper electrode forming step of forming an upper electrode on the dielectric film, whereby patterning of the lower electrode is not necessary, which simplifies the fabrication process. Micronized patterns can be formed.
The above-described objects are achieved by a method for fabricating a semiconductor device comprising the step of forming the iridium film or the iridium oxide film by the above-described thin film forming method.
The above-described objects are achieved by the method for fabricating a semiconductor device comprising: a first thin film forming step of selectively forming a first iridium film or first oxide iridium film in a set region of a substrate for the film to be deposited on; and a second thin film forming step of forming a second iridium film or a second iridium oxide film on an entire surface of the substrate having the first iridium film or the first iridium oxide film formed thereon.
The above-described objects are achieved by the method for fabricating a semiconductor device comprising: a plug burying step of selectively burying iridium film or iridium oxide film by the above-described thin film forming method in a through-hole formed in silicon oxide film formed on a surface of a substrate for the film to be deposited on; and an electrode forming step of non-selectively forming iridium film or iridium oxide film on the silicon oxide film with a plug buried in the through-hole to form an electrode connected to the plug, whereby only by changing deposition conditions for the iridium film and the iridium oxide film, burying the through-hole and forming the electrode can be concurrently conducted. Fabrication process for such a semiconductor device can be accordingly simplified.